Performance of carbide and ceramic tools in the milling of compact graphite iron - CGI

Abstract

Grey cast iron (GCI) is the most common material used in diesel engineCompact graphite iron is a material with intermediary properties between grey cast iron (GCI) and ductile cast iron (Sahm et al., 2002). Like in the GCI, the graphite particles in the CGI are flat, long, randomly oriented and interconnected. In the ductile iron they are in form of nodules (Warrick et al., 1999). However, as it can be seen in Fig. 1(b), the "worms" (as the graphite particles in the CGI are called) have something in common with the nodules of the ductile iron ( Fig. 1(a)), since both are much smaller than the graphite lamellas of the GCI (Fig. 1(c)). On the other hand, the morphology of CGI graphites is compact and with rounded tips, what makes the nucleation and growth of cracks more difficult than in the GCI. The sharp and lamellar graphites of the GCI with smooth surfaces (Fig. 1(c)) make this material more fragile than the other two (Löhe, 2005).The CGI alloys have good properties of mechanical strength, ductility, toughness, thermal shocks, damping and heat conductivity (Mocellin et al., 2004). These properties are better for the CGI part functioning, but make its machinability worse than the machinability of GCI.Compared with GCI, the CGI presents some advantages like reduction of the wall thickness of the parts for a same load, reduction of the safety factor due to a smaller variation of the cast properties, reduction of the fragile fractures during manufacturing, assembly and service due to its higher ductility and strength (Dawson, 1999).Compared with ductile cast iron, it can be said that with CGI it is easier to produce complex cast parts and the residual stresses are smaller due to the higher heat conductivity (what also helps to increase cutting tool life). Moreover, it presents smaller Young modulus and better machinability (Guesser, 2004). Milling of CGI engine blocksBesides the worm graphite particles, a certain percentage of spheroidal graphite nodules is also present in the CGI. As the nodularity increases, the material strenght also increases making the forces needed to cut the material higher. Moreover, with the nodularity growth, the heat conductivity decreases, decreasing machinabilty even more (Dawson, 2002).A factor that makes the engine blocks even more difficult to be machined is the great number of interruptions on the surface. Special care has to be taken in the mill cutter choice, because very positive tools reduce cutting force, but may generate tool life relatively lower when compared to the cutters with negative geometry, due to their small impact resistance.As the tool wears, workpiece surface roughness and flatness error increase. Besides tool wear, other important factors to obtain J. of the Braz. Soc. of Mech. Sci. & Eng.

State of the art review on the sustainable dry machining of advanced materials for multifaceted engineering applications: progressive advancements and directions for future prospects

“…The holes drilled showed best circularity for TiSiN/AlCrN coating at cutting speed of 150m min −1 [84]. The carbide tools show the best performance than ceramic tools when tested for same conditions in terms of too life [85].…”

Investigation of Drilling Machinability of Compacted Graphite Iron under Dry and Minimum Quantity Lubrication (MQL)

“…The main wear mechanism of the tool in the CGI machining process is within the adhesive because the casting surface of CGI consists of the ferrite, which is easy to bond with the cutting edge of the tool. In addition, abrasive wear has been observed in the prior study [10][11][12][13][14]. The flank surface of the cutting tool is the main region where tool wear can be found after the machining.…”

“…De Oliveira et al [10] conducted the CGI drilling experiments, which used three tool-based geometries of the cemented carbide drill with TiAlN-coating, and discovered that the main wear mechanism of the drill is abrasive wear in these experiments. Gabaldo et al [11] researched the tool wear mechanism and tool life in CGI milling using a cemented carbide and ceramic tool. In the finish milling, the tool made of cemented carbide had higher tool life than the ceramic tool.…”

Effect of Tool Coatings on Machining Properties of Compacted Graphite Iron

“…According to a study that comprehensively considered tool performance and price factors, cemented carbide tools are most well-suited for cutting CGI [ 10 ]. With the aim of improving the tool lifespan, researchers optimized the machining CGI machining process, mainly by considering the material [ 11 , 12 , 13 , 14 ], tool angle [ 15 , 16 ], tool coating [ 17 , 18 ] and cooling lubrication condition [ 19 , 20 ].…”